Telefunken USA: TF51 Tube Microphone

In any discussion of large-diaphragm tube condenser mics, five models seem to get mentioned more than all others combined: the Neumann U 47, U 67, and M 49, the AKG C12, and the Telefunken ELA M 251. To buy a clean, original example of any of these microphones requires a stretch into five-figure territory, with their high cost chiefly a reflection of their utility. People buy these expensive microphones to use, because they simply do the job in a way that's proven elusive to replicate.

Telefunken have spent the last eighteen years endeavoring to recreate the ELA M 251 in painstaking detail, using the best available components and methods. But this review isn't about that microphone – it's about the intelligence gathered in the process, and how that might translate into a more affordable package like the Telefunken TF51.

We should be clear that "more affordable" does not in this case, mean "cheap." Although the TF51 isn't the company's flagship model, it's positioned as a solid mid-priced microphone with some luxury appointments that can excel in professional environments. The first of these appointments are apparent immediately upon opening the fully-accessorized case: 7-pin XLR and power cables, a compact-but-sturdy power supply unit (with pattern selector), a soft mic cover/bag, and a pair of stand mounts (both fixed and suspended). The TF51 is part of Telefunken's new Alchemy Microphone Series, which also includes the TF29 Copperhead and TF39 Copperhead Deluxe, as well as the TF47 (a combination of design elements from the U 47 and M 49).

The TF51's decidedly contemporary exterior is attractive, but I couldn't resist unthreading the base, sliding off the body shell, and having a look at what's underneath. The orderly layout and high-quality polystyrene capacitors made a good first impression, but I was most interested in three key components. Tube condenser microphones are simple devices. A special variable capacitor (the capsule) has a conductive diaphragm that, when influenced by sound, creates minuscule charge and discharge currents. A vacuum tube and transformer then boost this tiny signal's amplitude and lowers its impedance, rendering it suitable for the input of a mic preamp. Those three parts – the capsule, tube, and transformer – perform the bulk of the work occurring in the microphone, and their quality will do much to determine whether or not the microphone sounds any good. They also tend to be expensive bits, so if a microphone is to be both good and affordable, managing their cost in the smartest way is critical.

By examining the included 12AY7/6072 tube's mica spacers and plate structure, I quickly determined that it was manufactured by New Sensor Corporation in Saratov, Russia. While no new production tube can compare to the vintage GE "five-star" 6072A tube revered by 251 purists, this is likely the best currently-manufactured 12AY7 type. Reaching out to Telefunken, I confirmed that they improve the odds by employing a 48-hour burn-in on each tube before testing for performance with an Audio Precision analyzer. Two silicone O-rings apply pressure to the glass envelope near the mica spacers (likely as a hedge against vibration-induced microphonic behavior). This was probably a wise inclusion, as the New Sensor Corporation tubes' mechanical stability tends to fall well short of the aforementioned triple-mica GE varietal. All in all, the TF51's tube strategy is quite sensible for a mic designed for accessible scale production. Those who prefer NOS 12AY7s can always experiment with alternatives – the stock tube is socketed with just enough room for an easy swap.

The capsule is always the tricky bit in more affordable microphones, and here Telefunken employs a similar strategy: endeavor to source the best available imported part, then employ rigorous selection methods. While the flagship ELA M 251 uses a capsule made in Telefunken's Connecticut laboratory, the TF51 has its capsule built in China to Telefunken's specifications before being quality-controlled in house. As with the CK12 capsule that sits atop the vintage ELA M 251, the TF51's capsule is edge-terminated in the Austrian tradition. However, it's only loosely based on the original, being of a different construction and utilizing a different backplate hole configuration.

Haufe, the German company that made the transformers in many original ELA M 251s, still exists (at least in name) and were tapped for a custom-spec unit loosely based on the original T14/1. Telefunken claims that some tweaks to the design were made to optimize performance, including the provision for a touch more low-frequency extension.

But enough tech-speak – what does it sound like? My first test drive was a vocal by indie pop artist Denitia. I'd previously found an excellent match for her voice: a circa 1972 silver AKG C414-comb with an exceptional brass-ring CK12 (not to be confused with the common nylon-ring iteration). I positioned the two mics headbasket-to-headbasket before carefully matching gain on a pair of Neve 31102 channel strips.

Each was very good, and I could've effectively used either, but they had subtly different identities. The old AKG C414, with its vaunted brass capsule, showed a bit more dimension and complexity as well as a top end that was airier in its extension. The TF51 felt firm and forward, with an upper midrange that was edgier and more assertive; its bottom end tighter and more-contained. Overall, the TF51 struck me as a bit more sharply focused and less overtly seductive. This is not a criticism, necessarily – while I chose the AKG C414 for the leads, the TF51 got the nod for background vocal stacks. Its focused low end was tidier and effectively kept things from getting too bloated as numerous vocals were layered up.

Trying the TF51 on other sources like piano and mono drum overhead yielded similar impressions: it's articulate and bright, but mostly a good kind of bright, which can be elusive in many affordable mics. We have (and like!) a pair of the now discontinued Blackspade UM17Rs, and this mic punches in the same weight class: it's one of the better options in a tube LDC for a little under two grand. If you have a studio full of five-figure vintage German and Austrian mics, the TF51 might be justifiably overlooked. But if you need to grow a small mic locker, or step into the mid-priced tube condenser price bracket for the first time, it would be easy to do worse (and hard to do substantially better) for the money.